Extensive articular cartilage damage is treated typically by making a small hole in the damaged area using a drill, or an awl to stimulate bleeding from bone marrow thereby introducing bone marrow mesenchymal cells into the joint. Applying a load, however, to the damaged part soon after the operation poses a risk of damaging still immature tissues.
Patent Literature 1 discloses an example of an external fixation device which can be utilized in such a treatment of an articular cartilage damage. The external fixation device includes ball joints and a gear box, sandwiches the joint and mechanically fixes two sides of the joint in order to protect the damaged part, so that joint bone parts are separated from each other and the damaged part will have a reduced load. Then, with the external fixation device attached, the patient moves the joint.